The invention concerns a method for determining a distance to a target object, wherein electromagnetic waves in the form of an outgoing signal are transmitted by a transmitter and at least one part of the outgoing signals is reflected on the target object and is received by a receiver as an incoming signal, wherein evaluation of the incoming signal takes place as a function of a reference signal, with the reference signal having a known phase difference with respect to the outgoing signal and the same frequency as the outgoing signal.
The invention further relates to a device for determining a distance to a target object as claimed.
Conventional methods and devices of this type use a phase difference between an incoming signal and a reference signal caused by the different signal path lengths of the outgoing and incoming signals and the reference signal to determine the distance to the target object. However, the accuracy of such a distance determination is only within one wavelength of the incoming signal used.
With another known method, an outgoing signal with increasing frequency, a so-called chirp signal, is transmitted and correlated with a corresponding incoming signal reflected on a target object. The differential frequency of both signals is proportional to the distance of the target object. Particularly disadvantageous in this method is the spatial resolution for determination of the distance of the target object which, at a frequency of the outgoing signal of approximately 24 GHz and with a chirp bandwidth of approximately 200 MHz, amounts to only approximately 0.75 m. With a typical evaluation in the spectral range, position accuracies in the decimeter region can be achieved. For many close-range applications, such as for distance detection in the field of motor vehicles, such low spatial resolution and position accuracy are unsuitable.
Accordingly it is the object of the present invention to improve a method and a device of the above-mentioned kind such that both the range accuracy as well as the position resolution or accuracy of the distance determination can be improved without simultaneously increasing the complexity of the device required for this purpose.